The present invention relates to a soft metal that is resistant to corrosion and is excellent in durability, such as stainless steel, iron base alloy, titanium, titanium alloy, aluminum, aluminum alloy, brass, copper, copper alloy, magnesium, and magnesium alloy, a method of producing the same, a decorative article using the same, and a method of producing the decorative article.
Since soft metals including stainless steel, iron base alloy, titanium, titanium alloy, aluminum, aluminum alloy, brass, copper, copper alloy, magnesium, and magnesium alloy are light in weight and inexpensive, these metals are worked into a wide variety of components for use in various fields. Examples of a soft metal article formed by processing the soft metals include decorative articles of wristwatch, such as a wristwatch case, wristwatch bezel, wristwatch case back, wristwatch band, clasp, crown, and so forth, and articles (hereinafter referred to as xe2x80x9cdecorative articlesxe2x80x9d) which are required to have decorativeness in external appearance, including a pendant, pierced earring, earring, ring, the frame of eyeglasses, tie-pin, cuff links, and so forth.
Meanwhile, the soft metals are inferior in terms of impact resistance because the surface hardness thereof is as low as not more than Hv=200 of Vickers hardness, thereby rendering the surface thereof susceptible to scratches. Further, the soft metals such as iron base alloy, aluminum, aluminum alloy, brass, copper, copper alloy, magnesium, magnesium alloy and so forth, except stainless steel, titanium, and titanium alloy, have a property susceptible to corrosion because of their poor corrosion resistance. Accordingly, with the aim of improving the impact resistance and corrosion resistance of the soft metals used as the constituent material of soft metal articles, attempts have so far been made to apply various surface hardening treatments for hardening the surface of the soft metal articles to the surface thereof. In the case of conventional decorative articles of wristwatch, a surface hardening treatment to coat the surface thereof with a film having high hardness and high corrosion resistance has been applied thereto. For example, a wristwatch case and wristwatch band are produced by coating the surface of brass as a base with a nickel electroplating film several tens of xcexcm thick, serving as an intermediate layer, and further, by coating the surface of the nickel electroplating film with a titanium nitride film several thousands angstroms (xc3x85) thick. The wristwatch case and wristwatch band as described have hardness at not less than Hv=1000 of Vickers hardness, exhibiting such high hardness and high corrosion resistance as showing no initiation of rust even when subjected to a salt spray test (SST) in accordance with JIS2371.
As methods of hardening the surface of the soft metal, there are generally available a method of forming a film coating the surface thereof, and a method of hardening the soft metal itself.
Examples of the method of forming a film on the surface of the soft metal include processes such as wet electroplating, ion electroplating, and so forth. As the wet electroplating, there are in widespread use nickel electroplating, nickel-phosphorus alloy electroplating, nickel-palladium alloy electroplating and so forth, however, a electroplating film formed by any of the processes described is soft and has not reached such a condition as to eliminate the risk of scratches being caused by impacts.
On the other hand, as the ion electroplating, there are cited processes of forming a film such as a hard carbon film, titanium nitride film, and so froth. However, since it is difficult to directly coat the soft metal, such as aluminum, aluminum alloy, brass, copper, copper alloy and so forth, with the hard carbon film, there is the need for forming the hard carbon film with an intermediate layer made of silicon, germanium, titanium and so forth, interposed therebetween. As a result, there exist more interfaces in this case due to the presence of the intermediate layer than in the case of directly coating the soft metal, resulting in a tendency that the hard carbon film is prone to peeling to that extent. Further, the titanium nitride film has poor adhesion property against the soft metal due to its high internal stress, so that the titanium nitride film has a property to be prone to peeling. Thus, with the ion electroplating, there has not been completely solved a problem that, whichever film is formed, the film is prone to peeling. Furthermore, there exists another problem that once the film, which is so important, is peeled, part of the soft metal itself is exposed, so that initiation of corrosion starts from that part, thereby rendering the soft metal unfit for use in the soft metal article.
As methods of directly hardening the soft metal itself, there have been known ion implantation, ion nitriding, gas nitriding, carburizing, and so forth. However, with any of those methods, since many hours are required in application of a hardening treatment, a soft metal article can not be efficiently produced. In addition, with the use of any of those methods, grain coarsening of the soft metal results because of high temperature needed for the hardening treatment, thereby involving the risk of occurrence of surface roughness. For example, upon application of a gas nitriding to a soft metal article after applying a mirror surface polishing thereto, there occurs surface roughness of 200 to 300 xcexcm due to the grain coarsening of the soft metal article after the gas nitriding, thereby causing a mirror surface to disappear, whereupon it becomes impossible to restore a mirror surface condition which has existed prior to the application of the gas nitriding even if a polishing is applied thereto thereafter, so that quality will be considerably impaired in terms of decorativeness of the external appearance.
The invention has been developed to solve the problems described above, and it is an object of the invention to provide a soft metal, a method of producing the same, a decorative article using the same, and a method of producing the decorative article, wherein the surface thereof is rendered insusceptible to scratches by enhancing impact resistance and initiation of corrosion is prevented by improving corrosion resistance so as not to impair decorativeness thereof.
A soft metal according to the invention is characterized in that a film made of an amorphous alloy is formed on the surface thereof.
Because a hard layer made of an amorphous alloy has excellent corrosion resistance against acid and alkali, and high mechanical strength, the surface of the soft metal is insusceptible to scratches, and initiation of corrosion. Further, if a pre-polishing is applied to the soft metal as an underlying base so as to have highly mirror polished surface, the soft metal can maintain such highly mirror polished surface as initially provided even after the formation of the hard layer made of the amorphous alloy because the amorphous alloy has highly mirror polished surface, so that decorative quality of the soft metal and a decorative article can be enhanced to that extent. Further, because the hard layer made of the amorphous alloy has excellent adhesion property with the soft metal, there does not occur peeling of the hard layer.
Further, the invention provides a soft metal with a film formed thereon, the film containing phosphorus and either platinum or palladium, and further, at least one element having homogeneous solubility with platinum or palladium, with the content of the phosphorus being in a range of about 15 to 25 atomic %.
The soft metal preferably contains nickel as one of elements having homogeneous solubility with platinum or palladium.
With the soft metal according to the invention, a film formed thereon may be made of an alloy selected from the group consisting of a platinum-copper-nickel-phosphorus alloy, platinum-nickel-phosphorus alloy, palladium-copper-nickel-phosphorus alloy, palladium-nickel-phosphorus alloy, palladium-platinum-copper-nickel-phosphorus alloy, and palladium-platinum-nickel-phosphorus alloy.
The invention also provides a soft metal with a film formed thereon, the film containing cobalt, and at least one element selected from the elements belonging to periodic table groups IVa, Va, or VIa, respectively, with the content of the cobalt being in a range of from about 55 to 95 atomic %.
With the soft metal described above, one element selected from the elements belonging to periodic table groups IVa, Va, or VIa, respectively, is preferably any of zirconium, niobium, and tantalum.
Further, with the soft metal according to the invention, a film formed thereon may be made of an alloy selected from the group consisting of a cobalt-zirconium alloy, cobalt-niobium-zirconium alloy, cobalt-niobium-titanium alloy, cobalt-zirconium-chromium alloy, cobalt-niobium-zirconium alloy, cobalt-niobium-zirconium-tantalum alloy, cobalt-niobium-zirconium-tantalum alloy, and cobalt-niobium-zirconium-titanium alloy.
Still further, the invention also provides a soft metal with a film formed thereon, the film containing boron and iron with the content of the boron being in a range of from about 15 to 25 atomic %.
The film of the soft metal described above preferably contains zirconium.
Yet further, with the soft metal according to the invention, a film formed thereon may be made of an alloy selected from the group consisting of an iron-cobalt-nickel-zirconium-boron alloy, iron-chromium-nickel-zirconium-boron alloy, iron-cobalt-nickel-niobium zirconium-boron alloy, iron-cobalt-nickel-tantalum-zirconium-boron alloy, iron-cobalt-chromium-nickel-niobium-zirconium-boron alloy, and iron-cobalt-chromium-nickel-tantalum-zirconium-boron alloy.
Further, with the soft metal according to the invention, a film formed thereon may be made of a gold-germanium-silicon alloy or a palladium-copper-silicon alloy.
A noble metal layer is preferably formed on the abovedescribed film of the soft metal, and the noble metal layer can be made of platinum or palladium.
The invention provides a method of producing a soft metal comprising the steps of disposing a soft metal and a target made of a predetermined alloy in a vacuum apparatus, and depositing atoms of metals composing the target on the surface of the soft metal, thereby forming a film made of an amorphous alloy composed of the atoms of the metals on the surface thereof.
Further, the invention also provides a method of producing a soft metal comprising the steps of disposing a soft metal and a target made of a predetermined alloy in the plasma atmosphere of a mixed gas containing an inert gas and a non-metallic element or a metalloid element, and depositing atoms of metals composing the target and atoms contained in the mixed gas on the surface of the soft metal, thereby forming a film made of an amorphous alloy composed of the atoms of the metals and the atoms contained in the mixed gas on the surface thereof.
Still further, the invention also provides a method of producing a soft metal comprising the steps of disposing a soft metal and a target made of a predetermined alloy in the plasma atmosphere of an inert gas, depositing atoms of metals composing the target on the surface of the soft metal, thereby forming an alloy layer composed of the atoms of the metals on the surface thereof, and applying a plasma treatment in the plasma atmosphere of a mixed gas containing an inert gas and a non-metallic element or a metalloid element, thereby implementing surface modification of the alloy layer so as to be turned into a film of an amorphous alloy containing atoms contained in the mixed gas as well.
As the mixed gas containing the non-metallic element or the metalloid element, a gas containing phosphoprus, germanium, boron, or silicon is preferably used.
The invention also provides a method of producing a soft metal, further comprising the step of forming a noble metal layer on top of the film made of the amorphous alloy after the abovedescribed step of forming the film made of the amorphous alloy on the surface of the soft metal.
Next, the invention further provides a decorative article made of the soft metal with the film made of the amorphous alloy, formed on the surface thereof.
Further, the invention provides a decorative article made of the soft metal with the film formed thereon, the film containing cobalt, and at least one element selected from the elements belonging to periodic table groups IVa, Va, or VIa, respectively, with the content of the cobalt being in a range of from about 55 to 95 atomic %.
With the decorative article described above, one element selected from the elements belonging to periodic table groups IVa, Va, or VIa, respectively, is preferably zirconium, niobium, or tantalum.
Further, with the decorative article according to the invention, the film formed thereon is preferably made of an alloy selected from the group consisting of a cobalt-zirconium alloy, cobalt-niobium-zirconium alloy, cobalt-niobium-titanium alloy, cobalt-zirconium-chromium alloy, cobalt-niobium-zirconium alloy, cobalt-niobium-zirconium-tantalum alloy, cobalt-niobium-titanium alloy, cobalt-niobium-zirconium-tantalum alloy, and cobalt-niobium-zirconium-titanium alloy.
Still further, the invention also provides a decorative article with the film formed thereon, the film containing boron and iron with the content of the boron being in a range of from about 15 to 25 atomic %.
With the decorative article described above, the film preferably contains zirconium.
With the decorative article according to the invention, the film formed thereon is preferably made of an alloy selected from the group consisting of an iron-cobalt-nickel-zirconium-boron alloy, iron-chromium-nickel-zirconium-boron alloy, iron-cobalt-nickel-niobium zirconium-boron alloy, iron-cobalt-nickel-tantalum-zirconium-boron alloy, iron-cobalt-chromium-nickel-niobium-zirconium-boron alloy, and iron-cobalt-chromium-nickel-tantalum-zirconium-boron alloy.
With the decorative article according to the invention, the film may be formed on the outer surface of an intermediate layer made of nickel or an nickel alloy.
Further, a noble metal layer is preferably formed on top of the film. The noble metal layer may be made of platinum or palladium.
Further, the invention provides a method of producing a decorative article, comprising the steps of disposing a decorative article and a target made of a predetermined alloy in a vacuum apparatus, and depositing atoms of metals composing the target on the surface of the decorative article, thereby forming a film made of an amorphous alloy composed of the atoms of the metals on the surface thereof.
Still further, the invention provides a method of producing a decorative article, comprising the steps of disposing a decorative article and a target made of a predetermined alloy in the plasma atmosphere of a mixed gas containing an inert gas and a non-metallic element or a metalloid element, and depositing atoms of metals composing the target and atoms contained in the mixed gas on the surface of the decorative article, thereby forming a film made of an amorphous alloy composed of the atoms of the metals and the atoms contained in the mixed gas on the surface thereof.
Yet further, the invention also provides a method of producing a decorative article, comprising the steps of disposing a decorative article and a target made of a predetermined alloy in the plasma atmosphere of an inert gas, depositing atoms of metals composing the target on the surface of the decorative article, thereby forming an alloy layer composed of the atoms of the metals on the surface thereof, and applying a plasma treatment in the plasma atmosphere of a mixed gas containing an inert gas and a non-metallic element or a metalloid element, thereby implementing surface modification of the alloy layer so as to be turned into a film of an amorphous alloy containing atoms contained in the mixed gas as well.
The method of producing the decorative article as described above preferably comprise further the step of forming a noble metal layer on top of the film made of the amorphous alloy after the step of forming the film made of the amorphous alloy on the surface of the decorative article.